Hydro-sedimentary model as a post-accidental management tool: Application to radionuclide marine dispersion in the Bay of Toulon (France)

The coastal city of Toulon, located in southern France, is the homeport of the French navy's nuclear-powered vessels, and is the largest nuclearized harbour in Europe. Therefore, an accidental release of radioactive material would have major consequences for the marine ecosystem and the economy of the region. A hydro-sedimentary model is presented to better understand the dispersion of a hypothetical release of radionuclides and to gain insights into the potential effects on the surrounding ecosystem, especially on sea sediments. The aim of the model is to provide the foundation of a management tool for experts and stakeholders in decision making in case of an accidental release. We simulate a numerical radionuclide discharge in the military harbour under several climatic conditions and we compute Cs-137, which might have substantial impacts on the marine ecosystem, and Pu-239 for its high affinity for solid phase. Results show that wind conditions and solid discharges from the Las River are the primary influences on sediment-bed contamination, and the hydro-sedimentary dynamics following the first days of release have an important influence on the distribution of radionuclides.